Thunderstone Search Appliance Manual

This performs a rewalk on the schedule specified. The rewalk action is the same as the one that can be started manually by clicking the GO button.
The Frequency defines how often to automatically rewalk. The
Hour defines which hour to start the rewalk for daily or weekly runs.

You can define multiple walk schedules for the same profile by
clicking the Add More Schedules link. This gives you more
granular control in setting schedules. For example, instead of
choosing between once a day and once an hour, you can
have a walk launch 3 times a day by making the 3 schedules

Daily at 8AM

Daily at 12PM

Daily at 4PM

To remove a schedule, set its Frequency to -None-.

See also Notify3.5.2.
If you are using "On Change"
see also Watch URL3.5.1.